Railway traffic controlling apparatus



Aug. ll, 1942.`

J. M. PELIKAN RAILWAY TRAFFIC CQNTROLLING APPARATUS `Filed Dec. 17,v1940' 2 sheets-sheet 1 Aug.y 11, 1942.

J. M. PELIKAN RAILWAY TRAFFIC` CONTROLLING APPARATUS u .hm www@ NAS@ N Am N 2 Sheets-Sheet 2 Filed Dec. 17, 1940 E mw @M f l gNToR lian H/.s'ATTORNEY Patented Aug. 11, 1942 RAILWAY TRAFFIC coNTRoLLING APPARATUSJohn M. Pelikan, Pittsburgh, Pa., assigner. to The Union Switch & SignalCompany, Swissvale, Pa., a corporation of Pennsylvania `ApplicationDecember, 17,1940, serial No. 370,433

. impractical. My present invention is van improvement on the inventiondisclosed in my -copending application SerialNo. 367,352, .filed onNovember 27, 1940, for Railway traffic controlling apparatus, now PatentNo. 2,251,689, issued August 5, 194:1. i i

One object of my invention is to provide a coded track circuit systemfor two-direction signaling on a single track without employing controlline wires. Another object of my invention is to provide a system of theabove character, which provides broken-down rail joint protection and inwhich 4traffic cannot be falsely set up in both directions at the sametime by stray currents. Other objects, purposes and features of myinvention will be. apparent from. the de-- scription which follows.

I accomplish the foregoing objects by providing each track circuit withtwo polarized code following track relays,A one at each end of theassociated track circuit, so arranged and connected that each relayoperates asa track relay only for its proper direction of traffic. Iestablish traffic direction in accordance with the polarity of the codedtrack current and employ directional stick relays for permittingfollowing traiiic movements and for preventing the set-up of confiictingroutes. By employing code, I'provide a plurality of signal indicationswhich permit following moves `through the single track stretch to beeasily and safely made.

I shall described one form of apparatus embodying mylinvention, andshall then point out the novel features thereof in claims.

Figs. la and 1b ofthe accompanying drawings when placed end to end withFig. 1a at the left, are a .diagramamtic view showing a stretch ofsingle track railroad equipped with apparatus embodying my invention.

Referring to the drawings, the stretch of single track between the twopassing sidings at locations D and E is divided by means of insulatedrail joints -2 into a numberV of track circuits such as 5T, 4T, TT, and8T. Entry into each of these track circuits is governed by a waysidesignal located at the entering end of the track circuit for theparticular traic direction. At F is a cut-section location which merelysubdivides the section of track between signals 4 and '8 into two trackcircuits for the purpose of `providing improved track circuit operation.

Each eastbound track circuit is provided with an eastbound codefollowing track relay at the entering end designated with a prefixcorresponding to the associated track circuit, andwith a normallydisconnected source of track circuit current at the leaving end. Eachwestbound track circuit includes. the, rails .of the eastbound trackcircuit but isprovided with its own westbound code following track relayat the entering end for that direction and with a normally disconnectedsource of current at the leaving end. The track relays are of the biasedtwo-position polarized type which Ypick up whenl energized with currentof one polarity but which remain in the released position to which theyare biased when current is 'discontinued or when current of the otherpolarity is supplied thereto. The purpose in maintaining the trackcircuit sources normally disconnected is to economize track battery,these sources becoming connected in response to the action taken bytheoperator or operators in setting up the apparatus for a trafc move inone or the other direction over the single track stretch.

At each signal location there is a suitable code transmitter CT whichmay be of the motor driven type and which supplies a or '75 coder byintermittently closing certain contacts designated as .|20 and 15,respectively, on the drawings at therate of 120 or 75 times 'per minute.Looking at location E, for example, and signal I0 which is shown atstop, the coder CTE which is energized from a source of current havingthe terminals B-C causes the flashing operation of the eastboundflashing relay IUEFR at a rate of either 120 or '75 times per minute,depending on the energized or deenergized condition of the home relayIDI-I for signal l0 which controls contact 42 in the circuit for relayIBEFR. Since the signal lil is at stop, the home relay IDI-I will bedeenergized and the back point of contact 42 will be closed so thatrelay IUEFR operates at '75 code, it being assumed that the trafficlever Il has been moved to its normal or N position for an eastboundtraflic move so that its N `contact is closed and the circuit for relayIIJEFR is therefore complete. Should signal I0 be occupying either thecaution or the clear. position, the front point of contact 42 of relayIDH would then be closed so that relay IIIEFR would be operating at arate of 120 times per minute. In order to simplify the disclosure asmuch as possible and make the circuits easy to follow, contact N oftraflic lever II, contacts |20 and 15 of coder CTE, as well as contact42 of relay IUI-I are shown removed from the apparatus by which they areoperated, but in each case these contacts are clearly identied by thefunction which operates them. The same is also true of other contacts inthe drawings, which for simplicity are identified by the relay whichoperates them rather than being shown in physical proximity to suchrelay.

Coding of the track circuit current itself is performed by theassociated flashing relay for the established trafc direction, andresponse of the track relay to this code causes operation of certaindecoding relays which control the signal indication and which code theadjoining,

track circuit so that relaying of the code will automatically continuefrom track circuit to track circuit until the headblock signal locationfor the desired traffic direction is reached. VAt location E, coding ofthe track circuit 8T is performed over the front point of contact 6 ofrelay IUEFR, which periodically connects the track battery TB across therails.

Looking next at location 1-8, the code following action of the eastboundtrack relay SETR in following 120 code will maintain the distant relay1-8DR energized by virtue of the resonated transformer-rectifier circuitwhich is tuned to pass impulses of 120 code but not 75 code. Theenergizing circuit for relay 1-8DR may be traced from one terminal B,over the front point of code following contact I2 of relay SETR, frontcontact I3 of the check relay 1--8CK, wire I4, and front contact I5 ofthe home repeater relay BEHP, to the tuned transformer and terminal C.Relay 1-8DR has a sufcient release interval to bridge the impulses ofthe 120 code. The check relay 1-8CK will be maintained energized oneither |20 or 15 code over an obvious circuit which includes the backpoint of the periodically operating contact I2 of relay BETR and theconstantly closed back contact I6 of theropposing track relay 1WTR.

Relay 8EI-IP is merely a repeater of the home relay 8EHR and ismaintained energized over the front contact I 1 of the latter relay.Relay SEHR is maintained energized on either 120 or 75 code over thefront point of contact I2 of relay GETR and front contact I3 of relay1-8CK. The sequence of operations beginning with the code followingaction of relay SETR is accordingly as follows: pick-up of relay 1-8CK(if this relay has not previously been picked up) pickup of relay SEHR;pick-up of relay 8EHP; and finally, pick-up of relay 1-8DR. It will beunderstood that all of these relays (except 1-8DR which responds only to120 code) are so designed as to remain picked up whether the code whichis effective inthe track circuit BT is 120 or 75. The home relay 1WHRfor the west-bound signal Twill obviously be deenergized because itscircuit will be open at the front point of ccntact I6 of the westboundtrack relay 1WTR. Accordingly, the repeater 1WHP will also bedeenergized. The Westbound track relay BWTR at the other end of trackcircuit 8T will not be operated by the discharge of any stored energy inthe track resulting from the track circuit code because such energy willbe of wrong polarity for pick-up of relay BWTR and will merely aid inmaintaining this relay released.

Under the above conditions, signal I will be at stop, its red lamp beingilluminated over an obvious lighting circuit which includes theterminals EN and EB of a suitable lighting source and back contact I8 ofrelay 1WHP. If the code is 120 (so that relay 1--8DR is up) signal 8will be at clear, with the green lamp energized over the front point ofcontact I9 of relay 1-8DR and the front point of contact 25 of relayBEHP. If the code is so that relay 1-8DR is released, signal 8 will beat caution, as shown, with the yellow lamp illuminated over the backpoint of contact I9 and the front point of contact 20.

At the location 1 8, I also employ directional stick relays aEsR) and'IWsR but since the operation of these relays comes into play onlyduring the passage of a train through the section, this operation willbe described hereinafter.v

I shall next describe how the code following operation of track relay8ETR causes code to be relayed into section 1T and into the remainingsections to the left for setting up an eastbound route over the singletrack stretch.

If the track relay SETR is following code, then this same code will berelayed into track circuit 1T by virtue of the operation of flashingrelay 8EFR. This relay has a 120 code operating circuit which includesone terminal B, wire 2l, contact |20 of coder CTS-I0, wire 22, frontpoint of contact 23 of relay 8EHP, and the winding of relay BEFR, to theother terminal C of the source. This 120 code operating circuit iseffective whether relay SETR is following 120 or 75 code because relayBEHP will be picked up in either case, thus completing the circuit. If,however, a train is occupying the track circuit 8T, then the operatingcircuit for relay SEFR will include contact 'I5 of coder CTB-40, frontcontact 24 of directional stick relay 8ESR, and the back point ofcontact 23 of relay BEI-IP which will now be deenergized. Thedirectional stick relay BESR will have been picked up as a result of theentry of the train into track circuit 8T, as will be explainedhereinafter, thus closing the 75 code circuit for relay 8EFR.

The periodic closing of front contact 25 of relay SEFR will impresseither 120 or 75 code from the track battery TB across the rails oftrack circuit 1T. Since location F is a cut section location, the 120 or75 code will be repeated into the adjoining track circuit 4T because ofthe code following response of the eastbound track relay 1ETR andtheinclusion of front contact 26 of this relay in the code supply circuitfor track circuit 4T. As a result, the eastbound track relay 4ETR willfollow either 120 or 75 code, as the case may be. If the code is 12'0,the group of relays 4-5CK, 4EHR, 4EHP, and 4-5DR will all be energized,in the same manner as described for the corresponding relays at location1 8. Accordingly, eastbound signal 4 will indicate proceed andwestboundsignal 5 will indicate stop.

Code will be relayed into track circuit 5T in an identical manner withthat described for track circuit 1T, so that the eastbound track relay5ETR. will follow either 129 or 75 code according as the stretch oftrack between signals 4 and 8 is unoccupied or occupied, respectively.

At each end of the single track stretch I have provided a traic leve-rhaving a normal position N for eastbound traffic and a reverse positionR nal lever having a neutral position `1L in which no contacts areclosed; a right-hand position r corresponding with eastbound traflic;and a lefthand position l corresponding with westbound traiilc. Thesesignal levers are designated as 2 l and 9 at the ends D and E,respectively, of the single track stretch.

Having described the individual apparatus and its operation at thediierent locations, I shall now assume that with the stretch D-E in itsnormal or unoccupied condition as shown, it is desired to set up theapparatus for an eastbound traffic move. To do this, each of the traiiiclevers I and II is moved to the N positiondunless the last movementrwaseastbound, in which case the traffic levers will already be occupyingthe N position), and the signal lever 2 is then moved to the 1'position. At the leaving end E of the stretch, relays SCK, SW1-IR, andSDR will all be deenergized because the energizing circuit, for each ofthese relays includes the reverse contact R of traflic lever II which isnow open. Accordingly, the opposing-signal L9 will indicate stop, itsred lamp being lighted over the back contact 28 of relay SWR1-I. Thenormal contact N of lever II will, as described hereinbefore, close the'15 code circuit for flashing relay IUEFR so that 75 code will beimpressed on the track circuit 8T over the front point of contact 6 ofrelay IUEFR. The reason why '75 code and'not 120 code is supplied tosection 8T is that a train is shown occupyingv the section immediatelyin advance of the single track stretch D--E, so that signal I8 is atstop and its home relay IUI-I is deenergized.

From this point on, the sequence of operations up to the response oftrack relay ETR will be clear from the previous description. Trackcircuits 1T, 4T, and 5T will all be receiving 120 code; signal 4 willindicate proceed; and signal B will indicate caution (since 75 code hasbeen assumed in the track circuit 8T due to the presence of a train justbeyond location E). The opposing signals 1 and 5 will obviously be atstop.

Looking now at the entrance end D, the check relay 20K will be picked upover a circuit which includes the normal contact N of traffic lever I,the right-hand contact r of signal lever 2, and the back point ofcontact 29 of periodically operating relay ETR. Relay ZEHR willaccordingly be picked up overthe contacts N and r of levers I and 2, inseries, front point of contact 29 of relay 5ETR, and front contact 3G ofrelay 20K. Since relay BETR is responding to 120 code, the decodingrelay 2DR will also be picked up so that the entering signal R2 willthen indicate proceed, its green lamp being lighted over the frontcontacts 3l and 32 of relays ZEI-IR and 2DR, respectively, in series.Relay IFR will, of course, not be flashing but will remain constantlydeenergized since its energizing circuit will be open at the reversecontact R 0f traffic lever I. It will be clear,

therefore, that relay EETR will remain constantly connected across therails, over the back contact 33 of relay IFR. With'the clearing ofsignal R2 by movement of the signal lever 2 to its r position, eastboundtraffic may proceed into the single track stretch.

I shall next trace the progress of an eastbound train through thesection, the traffic levers I and II having been placed at normal,signal lever 2 being to the right, and signal R2 indicating proceed. Asthe train enters the track circuit 5T, the track relay EETR becomesreleased, causing relays ZEHR and 2DR to release so that signal R2 goesto red. Relay 2CK will remain energized and the operator should .thenplace the signal lever 2 in its neutral or n' position in order to dropout relay ZCK so as to prevent any possibility cf signal R2 becomingcleared .after the train has vacated section 5T and the directionalstick relay 4ESR has picked up.

. When the train passes signal 4 which has'been at green, directionalstick relay 4ESR will pick up and will remain up thereafter until anopposing route is established. The pick-up of 4ESR occurs as follows.The opposing directional stick relay 5WSR is, of course, released andprior to the entry of the train into section 4T, relays 4EHR and 4EHPare both picked up. The shunting of track relay 4ETR will release4EI-IR, but for a short interval thereafter, relay 4EHP will remainpicked up because of its slow release interval. Accordingly, 4ESR willhave a pick-up circuit which includes back contact 34 of SWSR, backcontact 35 of 4EHR, and front point of contact 36 of 4EHP. A stickcircuit is now closed for relay 4ESR over back contacts 34 and 35 ofrelays BWSR and 4EHR, wire 31, and front contact 3B of relay 4ESR. Thesubsequent release of relay 4EHP closes a second stick circuit for relay4ESR over back point of contact 36 of relay 4EHP, wire 31, and frontcontact 38 of relay 4ESR.

The pick-up of 4ESR prepares a '75 code circuit for flashing relay 4EFRso that as soon as 4EHP releases, this flashing relay will be energizedover the 75 code contact of coder CTL-5, front contact 39 .of relayIIESR and back contact 4B of relay 4EHP. The operation of relay IIEFRwilll begin the coding of the track circuit 5T at 75 code over the frontpoint of contact 4I so thatthe response of relay EETR to this code assoon as the train vacates section 5T will cause signal R2 to go toyellow in order to permit a following train to enter the single trackstretch during occupancy thereof by the rst train.

During the time that the train occupies the sections 4T and 1T, relay4ESR will remain picked up and relay 4EI-lR will remain released. Signal4 will be at stop. As soon as the train fully vacates section 1T, thecoding action of relays 1ETR and 4ETR, in turn, followed by `pickup ofrelays 4EHR and 4EI-IP will cause release of the stick relay 4ESR. Sincerelay 4ETR is following '75 code, relay 4EHP will be up and relay4--5DRv willlbe down, so that signal 4 will indicate yellow or cautionat this time. The manner in which 75 code was supplied to section 1Twhen the train passed beyond signal 8 and shunted relay SETR will beclear from the description of the application of 7 5 code to section 5Twhen the train passed signal 4. That is, the pick-up of BESR and releaseof 8El-IP causes flashing relay EFR to operate at 75 code and to supplythis code to section 1T, whereupon it is relayed to the cut section 4T.Signal 8 will, of course, now be at stop;

Looking again at the signal 4 location, since relay 4EI-IP is now up,relay 4EFR will be following 12S code because it will be energized overthe 120 code contact of coder GT4- 5 and the front point of contact 40of relay 4EI-IP. Accordingly, 120 code will be supplied to section 5T sothat signal R2 will go to green, signal 4 being at yellow and tion 8T.

When the train fully clears sect-ion 8T and occupies .the adjoiningsection as shown in the drawings, 75 .code will be .supplied to section8T because .the flashing relay lliEFR will be energized over the backpoint of contact v42 of relay IH (whichis .the home relay for signal l!)of the section vnow occupied by the train) and the 75code contact ofcoder CTE. vOperation of relay SE'IR on 75 code will pick up relays EHRand 8EHP so that signal I8 will go to yellow. 'Ihe pick-up of SEHP willdropout BESR and will change the rate .of .operation of BEFR from l to12'0 vcode .so that 120 code will now be supplied to sections IT and 4T,causing signal 4 to go .to green. Since the train is now completely outof the single .track stretch, an opposing or Westbound route can besetup by reversing both traic levers I and Il .to their R positions andplacing signal lever 9 in its left-hand or Z position.

Since the `operations involved in setting up a westbound route and inthe passage of a westbound train over the section areV precisely thesame as already described for an eastbound movement except involving thecorresponding Westbound relays and signals, these operations will beclear vwithout further description.

summarizing briefly the operations which take place, moving the traiclever at the new exit end of the stretch to the position correspondingto the ,desired traftlc .direction causes code to be applied to thefirst track circuit at the new exit end, whichcode is relayedprogressively over the intervening track circuits .to cause .operationof .the code following track relay at the new entering end of thestretch. If now .both .the .traflic lever and .the signal lever at theentering .end are placed in .the position corresponding to the desiredtraino direction, the entering signal will clear .to permit entry of thetrain into the single track stretch. The opposing signals will be heldat stop by virtue of the position of ,the tralTic lever at the new exitend, following movements being permitted by means of directional stickrelay control which .establishes proper permissive signal indicationsinthe rear of the train. Once a trainY has entered the single trackstretch, the traic direction cannot be reversed by manipulation of thetraic levers, until such time as the train has fully cleared thestretch. A back-up move can, however, be permittedby proper movement ofthe traflic lever at that end of the stretch which serves as the exitfor the back-up move. For example, an eastbound train occupying thesection 4T may'back up and leave the single track stretch at location Dprovided that lever l is `iirst moved to the R position which causescode to be applied to section 5T by virtue of the code operation ofrelay IFR.

It Will be apparent from the foregoing that I have provided atwo-direction single track system of the A. P. B. type in which codedpolarized current is used for establishing trallic direction inaccordance with current polarity and for selecting the signalindications. Operation of a pair of trac levers, one at each end of thesingle track stretch, and a signal lever at the entering end, clears thesignals for a train movement through the stretch and permits followingtrains to enter but prevents any opposing move or a change inv theestablished direction until the single stretch is completely vacated.The polarity of adjoining track circuits, though shown alike i-n thedrawings, Afor simplicity, may be staggered for the purpose of providingbroken-down rail `joint protection. Because of the use of polarity code,opposing signals cannot lbe cleared at the same time through .the mediumof stray currents, or otherwise. Moreover, if desired, the system can becontrolled automatically from a remote point by a centralized tralliccontrol operator in which case the traino and signal levers would bereplaced by appropriate relays having the corresponding contacts andcontrolled either over a direct wire or over a coded line circuit.

Although I have herein shown and described only one form of apparatusembodying my invention, it is understood that various changes andmodifications may be made therein Within the scope of the appendedclaims without departing from the yspirit and scope of my invention.

Having thus described my invention, what I claim is:

1. In combination with a stretch of track over which tralic may move ineither direction, said stretch being divided into a plurality of trackcircuit sections, a rst and a second manually controlled traiiic leverat the rst and the second end respectively of said stretch, said levershaving a normal and a reverse position for selectively controlling thepolarity of the currentl supplied to said track circuit sections tothereby authorize eastbound and westbound traic movements respectively,an eastbound and a westbound polarized code following track relay foreach of said track circuit sections, said eastbound relay respondingonly to current of one polarity and ,said westbound relay respondingonly to current of the other polarity in any given track circuitsection, an eastbound and a westbound source of current for each of saidtrack circuit sections, said westbound track relays and westboundsources being ineffective under eastbound traic conditions and becomingeffective when westbound tranic conditions are established over thestretch, coding means effective when said second traic lever is moved toits normal position for supplying coded current of the proper polarityfrom the associated eastbound source to I the rails of the lasteastbound section to thereby cause code following response of theeastbound track relay Afor that section, means controlled by said lasteastbound track relay for supplying coded polarized current to the railsof the adjoining section from the eastbound source associated therewithto thereby operate the eastbound code following track relay for saidadjoining section and'in turn to relay the polarized coded current tothe rst eastbound section for operating the first eastbound codefollowing track relay, an eastbound headblock signal, a lever for saidsignal, and rmeans controlled by said signal lever when said firsttraflic lever is in its normal position and said rst eastbound trackrelay is following code for clearing said eastbound headblock signal.

2. In combination with a stretch of track over which traic may move ineither direction, said stretch being divided into a plurality of track Pcircuit sections, a rst and a second manually controlled traflic leverat the first and second end respectively of said stretch, said levershaving a normal and a reverse position for selectively controlling thepolarity of the current supplied to said track circuit sections tothereby authorize eastbound and westbound traic movements respectively,an eastbound polarized coded track circuit for each of said sectionsincluding an eastbound polarized code following track relay, a Westboundpolarized coded track circuit for each ing said `eastbound track-circuits with polarized coded current progressivelyfrom said second tosaid iirstend of the stretch, an 'eastbound headblock'signal, a leverfor said signal, 'and means controlled by said signal lever and the'rsteastbound track circuit and eiective when said rst controlled bysaid last-named eastbound track relay for alternately vdisconnecting thewestbound track relay of theadjoining section and supplying an impulseof polarized current to said adjoining section to cause code followingoperation of the associated eastbound track relay and to'relay polarizedcoded track circuit current to the rails of the first section to operatethe iirsteastbound code following track relay, aneastbound headblocksignal, and means effective when said rsteastbound track relay isfollowing code for clearing said eastbound headblock signal.4

leveris 'moved to itsnormal position for clearing said', eastboundheadblock signal'. l

3. 'In 4combination with a stretch 'of trackover which traffic Amay movein either direction', said stretch being divided vinto a plurality oftrack circuit sections, afirst and a se'cond manually controlled trafliclever at the `rstand second end respectively ofsaid stretch, said levershaving a normal and a reverse position for selectively controlling'the'polarity of the currentjsupplied to saiditiack circuit sectionsA tothereby `authorize 'coded track circuit current being oppositein` any ofsaid sectionsaccording as `eastbound orwestboundtraine-conditions `areestablished therethrough, meanseffective when Vsaid second traic leveris moved toits-normal position forV setting said westbound headblocksignal at stop and for 'energizing saideastbound track 4circuitsprogressively from said second to said first. end of the stretchwithpolarizedcoded current, means effective when said rst trafiic lever ismovedlto its normal position and said eastbound signal lever is operatedfor clearing said eastbound headblock signal, means effectivewhen saidrst trafl fic lever isA moved to its reverse position for settingsaidveastbound headblock signal at stop and -for "energizing saidwestbound track circuits progressively Vfrom 'said rst tol-said secondend of the stretch Vwith-polarized coded current, and

means effective when said-second traffic leverV is moved toits reverseposition and saidwestbound signal lever isoperated for clearing saidwest.- bound -headblocksignal. .l A Y. 4. In combinationwith a stretchof track over which traflicmay move in., either directionlsaid stretchbeingldivided into a plurality of track circuit sections, an. eastboundland alwestbound polarizedcode following track relay foreach of saidtrack circuit sections, each `of said relays being normally connectedacross the-railsof its associated section 4and beingoppositely polarizedin any given sectionmeans ,effectivewhen traflic conditions areestablished in the eastbound direction for alternately disconnecting thewestbound track relay associated with the last eastbound section andsupplying an impulse of current of the properpolarity to said lastsection to thereby-cause'code 'following operationV of the eastboundtrack relay for Vsaidlast section, means o. In combination with astretch of track over which traic may move'in either direction, saidstretchA being dividedl into a plurality of track circuitseetions,an'eastbound and a westbound polarized code following track relay foreach of said track circuit sections, each of saidA relays bein'glnormally connected across the rails -of its associated section, theeastbound and westbound rel'ays associated with a given section beingop- 'positely' polarized,V manuallyv controllable means hat theeastbound exit end of the stretch for supplying coded 'current of properpolarity t-o the last eastbound track circuit of said' stretch forcausing code following operation `of the eastbound vtrack relayassociated therewith, means controlled by said last-named track relayfor progressively relaying polarized coded current to the remainingsectionsof said stretch to finally cause code following operation of theeastbound track "tem havingopposing headblock signals at the endsthereof, a track circuit junction between said opposing signals, aneastbound and a westbound polarized codeiollowing track relay normallyconnected across the rails on opposite sides orsaid track circuitjunction respectively, means for supplying polarized coded current tothe track circuit associated with said eastbound relay to causef-/codefollowing operation thereof, and

means effectivefwhen said eastbound relay Ais following`code"for-*alternately disconnecting said -westbound rela'yfromA thetrack and substituting a source-of .current therefor to thereby supplypolarized coded'current to the rails associated with said westboundrelay. Y

i. '7; In atwo-direction single track signaling systern having at leasttwo adjoining track circuits between the 'ends of the single trackstretch, an `eastbound and a'westbound polarized code following trackrelay normally connected across the A"railsl ofsaid two adjoiningv trackcircuits respectively, means for supplying polarized coded cur- 'rent,to one-of said track circuits, and means -eiective Whenone` of saidrelays is following said coded current for alternately disconnecting theother of said relays from the track and substitutingV asource `ofcurrent therefor to thereby relay coded 'current into the other of saidtrack cir- ClltSr' 8.1 In atwo-direction single track signalingsysjternhaving atleast two adjoining track circuits between the ends `ofthe single track stretch, an eastbound and a westbound polarized codefollowing track relay normally connected across the rails of said twoadjoining track circuits respectively, means vfor supplying polarizedcoded current t one of said track circuits, and means effective when oneof said relays is following said coded current for alternatelydisconnecting the other of said relays from the track and connecting atrack circuit source of opposite polarity to that which would operatesaid other relay to thereby relay coded current into the other of saidtrack circuits.

9. In a two-direction single track signaling system having at least twoadjoining track circuits between the ends of the single track stretch,an eastbound and a westbound polarized code following track relaynormally connected a-cross the rails of said two adjoining trackcircuits respectively, means for supplying polarized coded current toone of said track circuits to cause said eastbound track relay to followcode, an eastbound home relay which remains energized whenever saideastbound track relay is following code, a coding relay energized over afront contact of said home relay, said coding relay having a backcontact included in the track connection of said westbound track relay,and means including a front contact of said coding relay for supplyingpolarized coded current to the other of said track circuits.

1Q. In a two-direction single track signaling system having at least twoadjoining ,track circuits between the ends of the single track stretch,an eastbound andV a westbound polarized code following track relaynormally connected across the rails of said two adjoining track circuitsrespectively, means for supplying polarized coded current to one of saidtrack circuits to cause said eastbound track relay to follow code, aneastbound home relay which remains energized Whenever said eastboundtrack relay is following code, a coding relay, a first energizingcircuit for said coding relay including a front contact of said homerelay for causing said coding relay to operate at a iirst code rate, asecond energizing circuit for said coding relay including a back contactof said home relay an-d elfective when and only when eastbound trafficconditions have been established over said stretch for causing saidcoding relay to operate at a second code rate, said coding relay havinga back contact included in the track connection of said westbound trackrelay, and means including a front contact of said coding relay forsupplying polarized 'coded current to the other of said track circuits.

1l. In a two-direction single track .signaling system having at leasttwo adjoining track circuits between the ends of the single trackstretch, an eastbound and a westbound polarized code following trackrelay normally connected across the rails of said two adjoining trackcircuits respectively, means for supplying polarized coded current toone of said track circuits to cause said eastbound track relay to followcode, an eastbound home relay which remains energized whenever saideastbound track relay is following code, a coding relay, a rstenergizing circuit for said coding relay includinga front contact ofsaid home relay for causing said coding relay to operate at a iirst coderate, an eastbound directional stick relay, a second energizing .circuitfor said' coding relay including a front contact of said directionalstick relay and a back contact of said home relay for causing saidcoding relay to operate at a second code rate, said coding relay havinga back contact included in the track con- Vnectionof said Westboundtrack relay, and means including a front contact of said coding` relayfor supplying polarized coded current to the other of said trackcircuits.

12. In a two-direction single track signaling system having at least twoadjoining track circuits between the ends of the single track stretch,an eastbound and a westbound polarized code following track relaynormally connected across the rails of said two adjoining track circuitsrespectively, means for supplying polarized coded current to one of saidtrack circuits to cause said eastbound track relay to follow code, achecking relay which remains energized whenever said eastbound trackrelay is following code, the energizing circuit for said checking relayincluding a back contact of said westbound track relay, an eastboundhome relay which remains energized whenever said eastbound track relayis following code, the energizing circuit for said home relay includinga front contact of said checking relay, a coding relay, an eastbounddirectional stick relay, a first energizing circuit for said codingrelay including a front contact of said home relay for causing saidcoding relay to operate at a rst code rate, a second energizing circuitfor said coding relay including a front contact of said directionalstick relay and a back contact of said home relay for causing saidcoding relay to operate at a second code rate, said coding relay havinga back contact included in the track connection of said westbound trackrelay, and means including a front contact of said coding relay forsupplying polarized coded current to the other of said track circuits.

13. In a two-direction single track signaling system having at least twoadjoining track circuits between the ends of the single track stretch,an eastbound and a westbound polarized code following track relaynormally connected across the rails of said two adjoining track circuitsrespectively, a coding relay for each of said track circuits, eachcoding relay having a back contact included in the track connection ofits associated track relay, and means effective when either of saidtrack relays is following code for causing operation of its associatedcoding relay to thereby supply polarized coded current over a frontcontact thereof to the adjoining track circuit.

14. In a two-direction single track signaling system having at least twoadjoining track circuits between the ends of the single track stretch,an eastbound. and a westbound polarized code following track relaynormally connected across the railsof said two adjoining track circuitsrespectively, means for supplying polarized coded current to one of saidtrack circuits to operate the track relay associated therewith, andmeans effective when said associated track relay is operating forperiodically and alternately disconnecting the other track relay fromthe track and connecting a source of polarized current across the railsof the other of said track circuits.

15. In a two-direction single track signaling system, a track circuit atthe entering end of the stretch of single track for a given direction oftrafc movement, a polarized code following track relay normallyconnected across the rails of said track circuit, a headblock signal atsaid entering end controlled by said track relay, means for supplyingpolarized coded current to said track circuit to cause operation of saidtrack relay, a trafc lever and a signal lever, a decoding relay havingan energizing circuit which includes a front contact of said track relayand a contact of each of said two levers, and means including a frontcontact of said decoding relay for clearing said headblock signal.

16. In a two-direction single track signaling system, a track circuit attheleaving end of the stretch of single track for a given direction oftraflic movement, a polarized code following track relay normallyconnected across the rails of said track circuit, a leaving signal atsaid leaving end, a home relay for said signal, a coding relay, a traiclever, means including a front contact oi said home relay and a contactof said traic lever for causing operation of said coding relay at afirst rate, means including a back contact of said home relay and saidcontact of the traic lever for causing operation of said coding relay ata second rate, and means including a contact of said coding relay forsupplying polarized coded current to the rails of said track circuit tothereby operate said polarized code following track relay.

JOHN M. PELIKAN.

